Printhead-carriage alignment and electrical interconnect lock-in mechanism

ABSTRACT

A printhead cartridge and carriage assembly ( 10 ) is provided comprising: a carriage ( 12 ); a snap-spring ( 62 ) for securing a printing cartridge ( 14 ) in postion on the carriage; and an interconnect strip ( 16 ) for supplying electrical signals to the cartridge, including a force loading spring pad ( 24 ) for urging a portion of the interconnect strip against a portion of the cartridge. The cartridge has top ( 32 ), bottom ( 34 ), sides ( 36, 38 ), front ( 40 ) and rear ( 42 ) surfaces and includes a printhead ( 44 ) on the bottom surface, an electrical contact strip ( 46 ) on the back surface connected to the printhead, referencing pads ( 56 ) on the side surface, and a lip ( 64 ) on the back surface for accepting the snap-spring. Referencing surface ( 60 ) are provided for receiving the referencing pads on the cartridge. The spring pad urges the interconnect strip against the electrical contact of the cartridge. The printhead cartridge/carriage assembly of the invention requires only one hand of the operator to both insert and lock the cartridge in position. Further, the cartridge/carriage assembly provides simultaneous alignment of the printhead in the X, Y, and Z directions. Finally, contact between the printhead and the interconnect strip is reliably made each time the cartridge is inserted and locked in position, thereby ensuring proper nozzle firing each time.

The present application is a continuation of application Ser. No.07/113,101 filed on Oct. 23, 1987, entitled “Printhead-CarriageAlignment and Electrical Interconnect Lock-In Mechanism,” now abandoned.

TECHNICAL FIELD

The present invention relates to ink-jet printers, and, moreparticularly, to alignment of the printhead and carriage and anelectrical interconnect lock-in mechanism for controlling the printhead.

BACKGROUND ART

In ink-jet printing technology, a printhead, comprising a plurality ofnozzles in a nozzle plate, is fluidically associated with a reservoir ofink. The printhead is mounted on one end of a print cartridge and thereservoir is provided inside the cartridge. Reference is made to U.S.Pat. No. 4,755,836, issued to Ta et al. on Jul. 5, 1988, and assigned toHewlett-Packard Company.

An interconnect means is provided, which carries electrical signals froma microprocessor in the printer to the printhead. For thermal ink-jetprinters, these signals provide a current to resistors associated withthe nozzles and thus control the heating of specific resistors, which inturn form droplets of ink. The droplets of ink are expelled through thenozzles toward a print medium, such as paper. The particular pattern ofresistor heating controls the pattern of characters formed on the printmedium.

The print cartridge is supported in a carriage, which is adapted to movebidirectionally, normal to the movement of the print medium through theprinter. The carriage movement is controlled by a motor and anassociated belt drive, with the motor controlled by the microprocessor.

Insertion of an ink-jet cartridge into the carriage often necessitatesuse of two hands or two operations. Further, many cartridge/carriageconfigurations do not provide simultaneous alignment of the nozzle platein the X, Y, and Z directions. Finally, contact between the printheadand the interconnect means must be reliably made, in order to ensureproper nozzle firing.

Accordingly, it is desired to provide a cartridge/carriage assembly thatincludes the foregoing advantages without the limitations of the priorart.

DISCLOSURE OF INVENTION

In accordance with the invention, a printhead cartridge and carriageassembly is provided comprising:

(a) a carriage;

(b) means for securing a printing cartridge in position in the carriage;and

(c) interconnect means for supplying electrical signals to thecartridge, including force loading means for urging the interconnectmeans against the cartridge.

The cartridge has top, bottom, sides, front and rear surfaces andincludes a printhead on the bottom surface, a contact on the backsurface connected to the printhead, referencing pads on the sidesurfaces, and a lip on the back surface for accepting a snap spring forlocking the cartridge in position in the carriage. The securing meansincludes the snap spring and means for receiving the referencing pads onthe cartridge. The force loading means urge the interconnect meansagainst the contact of the cartridge.

The printhead cartridge/carriage assembly of the invention requires onlyone hand of the operator to both insert and lock the cartridge inposition. Further, the cartridge/carriage assembly provides simultaneousalignment of the nozzle plate in the X, Y, and Z directions. Finally,contact between the printhead and the interconnect means is reliablymade each time the cartridge is inserted and locked in position, therebyensuring proper nozzle firing each time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an assembled carriage/cartridgeassembly, together with electrical interconnect thereto;

FIG. 2 is an exploded side elevational view showing the assembly of theelectrical interconnect and an elastomeric support in the cartridge;

FIG. 3 is a perspective view, partly cut-away, of the elastomericsupport;

FIG. 4 is a front elevational view of the carriage;

FIG. 5 is a side elevational view of the carriage, without thecartridge;

FIG. 6a is a cross-sectional view of the assembly depicted in FIG. 5,showing the cartridge inserted into the carriage, but not locked intoplace;

FIG. 6b is a view similar to that of FIG. 6a, but showing the cartridgelocked in position;

FIG. 7 is a view similar to that of FIG. 6b, but showing a greatlyenlarged view of the electrical interconnect and elastomeric supportassembled in the carriage;

FIG. 8 is a side elevational view similar to that of FIG. 4, but withthe cartridge chute removed in order to show the positioning of theelectrical interconnect in the carriage; and

FIG. 9 is a perspective view of the cartridge, showing the printheadelectrical contact, which provides electrical connection to theresistors in the printhead, and the reference pads.

BEST MODES OF CARRYING OUT THE INVENTION

Referring now to the drawings wherein like numerals of referencedesignate like elements throughout, a print cartridge/carriage assembly,denoted generally at 10, is shown in FIG. 1. The assembly 10 comprises acarriage 12 in which a print cartridge 14 is depicted, locked intoposition. An interconnect strip 16 provides electrical signals from amicroprocessor (not shown) to the cartridge 14, as discussed more fullybelow.

As shown in FIG. 2, the carriage 12 comprises a base support 18 and achute 20 affixed thereto by fastening means 22. The carriage 12advantageously comprises a glass-filled, carbon-filled,polytetrafluoroethylene-filled, silicon-filled polycarbonate.

The interconnect strip 16 and a spring pad 24 are sandwiched by thesupport 18 and a chute 20. The spring pad 24 comprises a resilient,elastomeric material and, as seen in FIG. 3, comprises a plurality ofresilient bumps 26. The spring pad 24 is seated in a depression 25(shown in FIG. 4) in the carriage base support 18, behind a portion ofthe interconnect strip 16, as described more fully below.

The base support 18 and chute 20 are aligned in proper relationship bymolded-in features such as pips 27, which engage through correspondingopenings in the interconnect strip 16 into opposed openings in the othermember.

The interconnect strip 16 comprises a strip of flexible dielectricmaterial, carrying a plurality of electrically conducting lines 28, asseen more clearly in FIG. 8. The conducting lines 28 terminate in convexcontact bumps or dimples 30, which are configured in a particularpattern.

The bumps 26 on the spring pad 24 are configured in the same pattern asthe contact dimples 30 on the interconnect strip 16. As seen in FIG. 7,the spring pad bumps 26 provide a force loading means against thecontact dimples 30 to urge them against the cartridge 14.

The cartridge 14 comprises top 32, bottom 34, sides 36, 38, front 40 andback 42 surfaces. The cartridge 14 advantageously comprises a modifiedpolyphenylene oxide.

A printhead 44 is provided on the bottom surface 34. The printhead 44comprises a plurality of resistors (not shown) associated with aplurality of nozzles (not shown) formed in a nozzle plate (not shown).Ink (not shown) is stored in a reservoir interior the cartridge 14.

The cartridge 14 also includes a contact strip 46 on the back surface42, which wraps around to the bottom surface 34 to provide a pluralityof conducting paths or traces to the resistors. In particular, eachresistor is supplied by an electrical signal along a unique conductingpath. The contact strip 46 includes a plurality of concave contact pads48, which are arranged in the same pattern as the convex contact dimples30 on the interconnect strip 16. Locking of the cartridge 14 in thecarriage 12, as described in greater detail below, matches up thecontact dimples 30 with the contact pads 48, to provide an electricalpath from the microprocessor to each of the resistors in the printhead44.

The contact strip 46 comprises a flexible material having a plurality ofelectrical traces thereon. Preferably, a tape automated bond (TAB)circuit of the type manufactured and sold by 3M Company (Minneapolis,MN) is employed.

The top surface 32 of the cartridge 14 is provided with a pair of fingergrips 50a, 50b. The larger finger grip 50a terminates in a V-shapedmember 52a, which may be provided with an arrowhead insignia to denotethe proper direction of orientation of the cartridge 14. When thecartridge 14 is locked in the carriage 12, the cartridge is received bya similarly shaped surface on the carriage to provide a visual referencefor proper orientation. Lock-out ears 54 further act to preventmis-orientation of the cartridge 14 in the carriage 12.

Reference pads 56, seen more clearly in FIG. 9, are provided on thecartridge 14 near the base thereof. In particular, two sets of referencepads 56 are provided; these comprise sculpted surfaces that align thenozzle plate in the X, Y and Z directions. The X reference pad 56x is asurface parallel to the side surface 38. (There is only one X referencepad 56x, since the carriage 12 is provided with a side spring 58 whichurges against the opposite side surface 36 to force the cartridgeagainst one side of the chute 20.) The Y reference pad comprises padscomprise the upper vertical surface surfaces 56y of the sculpted surfacesurfaces. The Z reference pad comprises pads comprise the innerhorizontal surface surfaces 56z of the sculpted surface surfaces. Thejunction of 56y and 56z comprises a pivot or rotation point 56r, aboutwhich the cartridge 14 rotates during the lock-in operation.

Downwardly depending L-shaped members 60a, b on the support base 18 eachcooperatively engage one of the reference pads 56 in mating association.A snap-spring 62 in the upper portion of the chute 20 engages a ledgemember 64 on the back surface 42 of the cartridge 14.

The L-shaped members 60a, b provide reference surface against which thereference pads 56 of the cartridge bear. In particular, reference pad56x bears against reference surface 60x on member 60a (the member on theopposite side of the side spring 58). Reference pads 56y push backagainst reference surfaces 60y (shown in FIG. 2). Reference pads 56zbear down on reference surfaces 60z.

The snap-spring 62 is housed in a molded-in feature 66 of the cartridgesupport base 18. A mating housing 67, which sits above the snap-spring62 when the base 18 and chute 20 are assembled, includes an inwardV-shaped surface 66a, which receives the similarly-shaped surface 52a ofthe cartridge 14. The rear of the housing 66 comprises a finger grip 68.The front of the cartridge chute 20 is also provided with a finger grip20b.

The support 18 of the carriage 12 includes a bearing 70, which isassociated with a carriage rod (not shown). The carriage rod ispositioned substantially parallel with the paper drive axis (not shown),and permits bidirectional movement of the carriage 12 therealong. Thecarriage 12 is moved by a belt (not shown), attached to the carriage bya belt attachment 72. The belt is attached to a carriage drive motor(not shown), which is controlled by the microprocessor.

A reference means, or slider bump, 74 rides on the surface of a carriageguide 76. The weight of the carriage 12 preloads the slider bump 74against the carriage guide 12, thereby making constant contact. Theslider bump 74 comprises a low-friction, long wearing material and maybe a separate piece or a molded-in feature of the carriage 12. Theslider bump 74 serves to maintain the printhead 44 a constant, fixeddistance from the print medium.

The carriage base 18 also includes an interposer arm 78 secured in ashaft 80. The function of the interposer arm is related to mechanicallytriggering certain features in the service station where the assembly 10resides in between printing operations, and is not relevant to theinvention herein.

The printhead lock-in mechanism is considered unique, since itsimultaneously aligns the nozzle plate in the X, Y, and Z directions andaligns, wipes, and loads the contact pads of the electrical interconnectstrip 16. This is accomplished with no additional bail, latch or leverarm, as seen on other ink-jet printers. The alignment of the nozzleplate and the loading of the interconnect strip 16 occurs when the userrotates the cartridge 14 in the direction of the arrow 74 (FIG. 6a),about the pivot point 56r. The user does this by squeezing the cartridgethumbhold 50a and the carriage finger hold 68 between the thumb andforefinger.

Before the user can squeeze the cartridge 14 into its locked-inposition, the user must be able to easily drop the cartridge into thecarriage chute 20. The springs 58, 62 which align the cartridge 14 donot apply any force to the cartridge until the cartridge begins torotate into the locked-in position (shown in FIG. 6b). This leaves anunobstructed path for the user to easily drop the cartridge 14 into thepre-rotation position, depicted in FIG. 6a. However, the side-kickerspring 20 applies light force when inserting the cartridge 14.

The cartridge 14 rotates about the reference pads 56, specifically,point 56r. As the user rotates the cartridge 14, the alignment functionsare performed before the electrical interconnect strip 16 is loaded.First, one side 36 of the cartridge 14 engages the molded-in carriageside spring 58. This spring 58 references the cartridge 14 in the Xdirection by pushing the cartridge sideways until the X reference pad56x is touching the X reference pad 60x on the cartridge. The result isan accurate, no slop alignment of the nozzle plate in the X direction.

The next action to occur is the alignment in the Z direction. As therear ledge 64 of the cartridge 14 encounters the rear metal snap-spring62, the spring pushes the cartridge in the Z direction until the Zreference pads 56z are in contact with the Z reference pads 60z on thecarriage 12. The result is an accurate, no slop registration of both theelectrical interconnect 16 and the nozzle plate in the Z direction.

As the cartridge 14 continues to rotate about the rotation point 56rinto position, the electrical interconnect concave contact pads 48 onthe cartridge contact 46 get wiped slightly by the convex contactdimples 30 on the carriage interconnect strip 16. This offers improvedreliability over the dimpled interconnect on prior art printers, becausethe oxides and contamination are wiped off the contacts 30 and 48 beforethe interconnect 16 is loaded.

The wiping action is followed by the alignment of the cartridgeelectrical contact pads 48 in the X direction. This occurs when thecartridge's outer rear heel lock tabs 84a, c engage the sides 86a, c ofthe heel lock slot 86 on the carriage 12. The interconnect strip 16 onthe carriage 12 is referenced accurately to the heel lock slot 86 bypins 27, thereby providing the required alignment of the interconnectstrip to the cartridge's electrical contact pads 48. The contact strip46 is fastened, such as by glue or adhesive, to the cartridge 14 and isreferenced by an assembly machine.

Finally, the cartridge 14 is aligned accurately in the Y direction. Theelectrical interconnect's rubber spring pad 24 on the carriage 12 mustbe deflected the proper distance in the Y direction in order to maintainthe required contact force. In the back 42 of the cartridge 14, therubber spring 24 pushes back against the electrical contacts 30 and 48so that the Y reference pads 56y on the cartridge contact the Yreference pads 60y on the carriage. This maintains the necessary forceon the contact pads 48 located on the contact strip 46, on the rearsurface 42 of the cartridge 14. This also provides an accurate Yregistration of the nozzle plate as well as controlling the rotationalalignment of the nozzles.

At the top 32 of the cartridge 14, the required contact force in the Yand Z directions is maintained by the rear snap-spring 62. As thecartridge 14 rotates into the locked-in position, the rear lip 64 of thecartridge 14 deflects the rear spring-snap 62 and passes over anover-center point 62a (FIG. 6a) on the snap-spring. The snap-spring 62is designed to apply about 70% of its force in the Y direction. This isthe force required to maintain the electrical interconnect 16 in therear 42 of the cartridge 14.

As the cartridge 14 passes the over-center point 62a on the rearsnap-spring 62, the cartridge makes an audible “snap”, signalling to theuser that the cartridge is in the proper locked-in position. The forceof the rubber interconnect spring pad 24 is adequate to hold thecartridge into its accurately aligned position under the largeaccelerations and shock loads the cartridge encounters in normalprinting operations.

To remove the cartridge 14 from the carriage 12, the user simply rotatesthe cartridge by squeezing the cartridge finger hold 50b and thecartridge thumb hold 20b between the thumb and forefinger. The rearledge 64 on the carriage 14 deflects the rear snap-spring 62 until thecartridge over-centers into the unlocked position. There is an audible“snap” which tells the user that the cartridge 14 can now be lifted outof the carriage 12 for disposal.

INDUSTRIAL APPLICABILITY

The print cartridge/carriage assembly disclosed herein is suitablyemployed in ink-jet printers, particularly thermal ink-jet printers.

Thus, there has been disclosed an ink-jet print cartridge/carriageassembly which is easily assembled and disassembled, with reproduciblyaccurate registration of the cartridge in the carriage. Various changesand modifications of an obvious nature will be readily apparent to thoseof ordinary skill in this art, and all such changes and modificationsare considered to fall within the scope of the invention, as defined bythe appended claims.

What is claimed is:
 1. A printhead carriage lock-in assembly (10) foruse with a cartridge (14) in a printer, for printing on a print medium,comprising: a. carriage means (12); b. said carriage means includingbase support means (18) for receiving the cartridge; c. said basesupport means depending into referencing means (60a, 60b), for aligningthe cartridge in proper printing position along at least two directions;d. said base support means further including retention means (62) forcausing the cartridge to be locked in position relative to said carriagemeans; e. electrical interconnect means (16, 24, 46), for supplyingcontrol signals to the carriage; f. the cartridge including a referencesystem (56) corresponding to, and generally coordinating with, saidreferencing system of said base support means, for providing properalignment to the cartridge during its positioning relative to saidcarriage means, and for causing the cartridge to be retained in positionduring the printing operation; g. said referencing means including apair of downwardly depending, spaced-apart, generally oppositelydisposed L-shaped members (60a, 60b), for engaging said reference systemof the cartridge; h. the cartridge including a rear ledge (64), and saidretention means including spring means (62) for engaging said rear ledgein order to retain the cartridge in a locked position; i. the cartridgefurther including a top portion (32), a bottom portion (34), andprinthead means (44) generally secured to said bottom portion; and j.said reference system (56) of the cartridge including two sets ofsimilar pads (56x, 56y, 56z), generally disposed near said bottomportion in a substantially symmetrical relationship relative to saidprinthead means; k. said reference pads pad (56x) abutting one of saidL-shaped members (60a); l. said reference pads (56y) abutting the otherboth L-shaped member members (60a, 60b); and m. the cartridge furtherincluding lock-out ear means (54), slightly protruding outwardly fromsaid top portion (32), for enhancing the orientation of the cartridgeinside said carriage means.
 2. A printhead carriage lock-in assembly forreceiving a cartridge having electrical contacts (46, 48) a contactstrip ( 46 ), electrically conducting pads ( 48 ), a reference system(56) and a plurality of print elements, the print elements beingdisposed out of the plane of the electrical contacts electricallyconducting contact pads ( 48 ), the printhead carriage lock-in assemblycomprising: a. carriage means; b. said carriage means including basesupport means for receiving the cartridge; c. said base support meansdepending into referencing means (60a, 60b), for aligning the cartridgeinto a proper printing position along at least two directions (x,y); d.said referncing referencing means generally coordinating with thereference system of the cartridge, for providing proper alignment to thecartridge during its positioning relative to said carriage means, andfor causing the cartridge to be retained in position during the printingoperation; e. electrical interconnect means, for supplying controlsignals to the cartridge electrical contacts electrically conductingcontact pads of the cartridge; and f. said electrical interconnect meansbeing disposed out of the plane of the cartridge electrical contactsprint elements to avoid obstructing the firing path of the printelements onto a print medium, to minimize contamination of saidelectrical interconnect means resulting from the firing of the printelements, and to allow for a desirable relatively close spacing betweenthe print elements and the print medium.
 3. The assembly as defined inclaim 2, wherein said referencing means includes a pair of downwardlydepending, spaced-apart, generally oppositely disposed L-shaped members(60a, 60b), for engaging said reference system of the cartridge.
 4. Theassembly as defined in claim 3, further including retention means (62)for causing the cartridge to be locked in position relative to saidcarriage means; and wherein the cartridge includes a rear ledge (64),and wherein said retention means includes spring means (62) for engagingsaid rear ledge in order to retain the cartridge in a locked position.5. The assembly as defined in claim 4, wherein said carriage meansfurther includes chute means (20), secured to said base support means(18), for helping guide the cartridge in position.
 6. The assembly asdefined in claim 4, wherein the cartridge further includes a top portion(32), a bottom portion (34), and printhead means (44) generally securedto said bottom portion; wherein said reference system (56) of thecartridge includes two sets of similar pads (56x,56y, 56z), generallydisposed near said bottom portion in a substantially symmetricalrelationship relative to said printhead means; wherein said referencepads pad (56x) abut abuts one of said L-shaped members (60a); andwherein said reference pads (56y) abut the other both L-shaped membermembers (60a, 60b).
 7. The assembly as defined in claim 5, wherein saidelectrical interconnect means includes an interconnect strip (16),disposed intermediate said base support means and the cartridge, andterminating in a plurality of dimples (30) disposed in a predeterminedarrangement, for effecting electrical contact with the cartridge.
 8. Theassembly as defined in claim 7, wherein the cartridge contacts include acontact strip (46) having a plurality of electrically conducting pads(48) are disposed in a predetermined array on the contact strip ( 46 )for effecting electrical contact with said interconnect strip (16);wherein said contact strip (46) provides a plurality of conducting pathsto said resistors generally terminating in said conducting pads.
 9. Theassembly as defined in claim 8, further including spring pad means (24)disposed intermediate said base support means (18) and said interconnectstrip (16), for forcing said interconnect strip against the cartridge,in order to maintain a good electrical interconnection therebetween. 10.The assembly as defined in claim 9, wherein said spring pad meansincludes a plurality of externally protruding bumps (26); and whereinsaid bumps are disposed in a generally similar arrangement to that ofsaid dimples (30) and said conducting pads (48) and in registrationtherewith, such that said bumps force said dimples against saidconducting pads, in order to maintain a good electrical contact betweensaid interconnect strip and the cartridge.
 11. A printhead carriagelock-in assembly (10) for use with a cartridge (14) in a printer, forprinting on a print medium, comprising: a. carriage means (12); b. saidcarriage means including base support means (18) for receiving thecartridge; c. said base support means depending into referencing means(60a,60b), for aligning the cartridge in proper printing position alongat least two directions; d. said base support means further includingretention means (62) for causing the cartridge to be locked in positionrelative to said carriage means; e. electrical interconnect means (16,24, 46), for supplying control signals to the carriage; f. the cartridgeincluding a reference system (56) corresponding to, and generallycoordinating with, said referencing system of said base support means,for providing proper alignment to the cartridge during its positioningrelative to said carriage means, and for causing the cartridge to beretained in position during the printing operation; g. said referencingmeans including a pair of downwardly depending, spaced-apart, generallyoppositely disposed L-shaped members (60a, 60b), for engaging saidreference system of the cartridge; h. the cartridge including a rearledge (64), and said retention means including spring means (62) forengaging said rear ledge in order to retain the cartridge in a lockedposition; i. said carriage means further including chute means (20)secured to said base support means (18), for helping guide the cartridgein position; and said chute means including spring means (58) forapplying a relatively light force against the cartridge, to help guideits alignment and positioning inside said chute means.